1. Field of the Invention
The invention relates in general to the protection of digital sound and picture objects against unauthorized reception and copying and in particular to how the protection against unauthorized reception and copying can be implemented in a uniform manner as regards broadcasting, local storage and the selling and distribution of recordings to consumers.
2. Description of the Related Art
Electrical transmission and storage of programs and presentations including images and/or sound has shifted or is shifting from analog to digital technology, the advantages of the latter being lower susceptibility to spurious effects and versatile error correction possibilities. The quality of a digital image and sound will not deteriorate in transmission, reception and storage in the same way as it does when using analog technology. Digital technology is already being widely used in the sales and distribution of audio and data recordings in the form of compact discs, or CDs. Computers apply digital magnetic storing of data in their mass memory units and digital broadcasting systems are in pilot stages. We can assume that in the future both the capacity and the exploitation of data transmission and storage will continue to increase.
Below, all digital sound and image recordings and transmissions handled as one entity will be called simply objects. An object may be a picture, sound effect, piece of music, film, animated program, radio program, multimedia program or other corresponding entity which can be transmitted, stored and reproduced to a user as such and/or together with other corresponding objects. By transmission it is meant especially broadcasting, where a transmitting station electrically distributes objects to a great number of receivers on a regular basis. By storing it is meant that the object or a period extracted from it is rendered into a form from which it can be later decoded to be reproduced to a user several times if required.
Computer programs can also be considered some kind of objects, even though they are not in the same way meant to be broadcast. Multimedia and interactive mass media becoming more popular, the boundary between the computer program as we know it and the radio or TV program, whether it is meant to be entertaining or educational, will become blurred. For instance, the digital audio broadcasting (DAB) system provides for transmitting objects that are broadcast in file format and loaded in the storage media of the receiving equipment to be later interactively reproduced to a user so that the user will have the opportunity to change the flow of the program.
Since digital recordings are easily duplicated, there has arisen a need to encrypt, or scramble, the objects in connection with transmission and storage so that their reception and reproduction without a permission from their copyright owners be as difficult as possible. The purpose of this arrangement is that the producer and/or distributor of an object get a certain remuneration from the receiver and/or user. It is common that a user acquires a decoding device or key with which the object can be descrambled for use. A so-called black box is known from the prior art which descrambles programs sent on TV channels liable to charges. A descrambling device may be controlled by a so-called smart card, for example, which contains the code words needed for descrambling. A similar method, where a scrambled transmission is descrambled using keys stored in a smart card, has been applied in digital data transmission in the GSM mobile telephone system, for example.
Scrambling and descrambling methods and devices according to the prior art are usually characterized in that they are channel specific which means the scrambling is directed to a particular transmission stream always in the same way regardless of what objects the transmission stream contains. The only options are switching the scrambling on and off, if e.g. a pay TV channel wants to send a particular film or program unscrambled so that it can be viewed by a larger audience. Copyrights, however, are always directed to individual objects and, therefore, methods according to the prior art cannot implement a pay system where the producers of objects acquired from different sources could be remunerated in any other way than if the transmitting station pays for the right to broadcast a particular object in its distribution network or coverage area.
Arrangements according to the prior art are also characterized in that a receiver who has at his disposal a descrambling device can without limitation store, duplicate and further distribute a particular object after having descrambled it. To safeguard the rights of parties producing objects and their transmission and distribution services it is essential that users could be obliged to pay a separate recompense for storing and duplicating an object.
In conjunction with computer software it is used a fixed key device, or a so-called hardlock, which usually comprises an electric circuit cast in a plastic housing that has to be inserted in the communications port of the computer for the program to be usable. With this arrangement it is to some extent possible to prevent the duplication of an object because an ordinary user cannot duplicate the hardlock and a duplicated program copy will not function without the hardlock. However, the arrangement is rather inflexible as the hardlock is tied to a particular version of a particular object, and it cannot be applied on a broader basis if the objects vary and change constantly as they do in a broadcast-type transmission.